1. Field of the Invention
The present invention relates to access port covering devices and, more particularly, to an improved, latching assembly which includes an interlock that is normally operated by the presence of a required component within the port.
On modern aircraft, various access ports are provided to enable inspection and operation of components and mechanisms which are located adjacent the exterior skin of the craft. Most if not all of these access ports require covers which can be secured and which form an effective, pressure tight seal so as to preserve whatever pressure differential may exist between the aircraft in flight and the surrounding environment.
2. Description of the Prior Art
Typically, a modern aircraft may have many access ports to enable filling or draining of onboard systems and, for that purpose the systems are provided with plugs and/or other closures which are wholly independent of the access port cap or cover. For example, most aircraft human waste management systems include an accumulation-type tank which contains a recirculating fluid that must be drained and/or flushed when the aircraft has landed.
A combination for this purpose has been disclosed, for example, in the patent to Lynch, U.S. Pat. No. 3,010,694, which teaches a sealing plug capable of remote actuation for engaging and disengaging the plug, together with an appropriate coupler and assembly which enables an operator to drain the tank conveniently into a waste line, without accidental discharge of the contents.
The patent shows a handle for both removing and replacing the sealing plug as a part of the drain conduit. In proper operation, after the tank has been drained and/or flushed, the plug is replaced, the assembly is disconnected from the aircraft, and the access port is closed.
There are, however, occasion when the operator who removes the plug to drain the tank fails or neglects to replace the plug after the tank has been drained. It is also possible that a different operator may remove the assembly from the aircraft assuming, erroneously, that the drain plug had been replaced even though the assembly was not removed from the aircraft.
In either event, the access port can be closed without the drain sealing plug in place. Since the access port cap generally includes a sealing gasket, the absence of the drain plug will not result in leaks of the tank contents to the environment while the aircraft is in flight or on the ground. Generally, the subfreezing temperatures encountered by the aircraft in flight assure that any liquid that might leak through the seal is immediately frozen and, if a plug is missing, an accumulation of frozen waste may develop adjacent the access port cap.
The problem is most acute when the aircraft lands and must be serviced. Since the access port cap must be opened before the coupling assembly can be attached to the drain, the opening of the access port cap in the absence of a sealing plug, may result in an accidental discharge from the tank before the coupling assembly can be attached to the discomfort of the servicing personnel.
It has always been deemed desirable, if not necessary, to provide means for securing the access port cap. Various latching assemblies have been provided in the past. Further, because the failure to replace a drain plug may be inadvertent rather than intentional, it has been deemed a useful modification to provide an interlock assembly which cooperates with a drain plug in place, so that the access port cap cannot be secured in the absence of a drain plug. However, if the drain plug has been lost or is so damaged that it cannot be reinstalled, then the interlock should be such that it can be defeated or overridden to permit a closure of the access port cap so as not to disable the aircraft.
Accordingly, it is an object of the present invention to provide an improved access port cap assembly with an interlock that prevents the operation of the latch in the absence of a required component such as a drain plug.
It is an additional object to provide a vehicle with an access port assembly having an interlock mechanism that can be defeated in the absence of a required component, so that the vehicle is not disabled by the lack of a non-essential component, such as a waste drain plug.
It is yet another object of the invention to provide, in an access port cap, a latching mechanism which includes an interlock that cooperates with a required component but which, if defeated in the absence of such a component, will signal the absence.